Fig. 6.

Numerical model set-up to investigate time-evolving subduction of a 6000 km wide subduction zone comparable to the South American subduction zone in a very large three-dimensional domain with a layered whole-mantle reservoir. a Three-dimensional perspective view. b Cross-sectional view through the centre of the subduction zone (symmetry plane in a). The model includes a layered negatively buoyant oceanic subducting plate with three layers with different viscosity (top, middle and bottom) and a layered continental overriding plate with two layers with different density (crustal layer and lithospheric mantle layer). Note that v _T⊥ = trench-normal trench velocity (oceanward retreat is positive), v _SP⊥ = trench-normal subducting plate velocity (trenchward is positive), W = slab width, ρ _UM = sub-lithospheric upper mantle density, ρ _LM = lower mantle density, ρ _SP = subducting plate density, ρ _C = continental crustal density, and ρ _LiM = lithospheric mantle density. See Methods section for more details